Abstract
In the present study, simulations of the lightning overvoltages propagation phenomenon in a typical 380 kV SF6 gas-insulated substation are presented. Influence of surge arresters installation on maximum-generated overvoltage peak values is illustrated. A new overvoltage mitigating passive device in a form of a high-voltage (HV) L-C filter is proposed. A process of its development and research is explained along with a simulation results. As demonstrated, the proposed device can be used in HV networks as an alternative or additional improvement for lightning overvoltages mitigation purposes. All simulations have been conducted using Matlab Simulink as well as EMTP/ATP software packages.
1 Introduction
In high-voltage (HV) power systems, Insulation Coordination studies are needed in order to minimise the probability of equipment failure because of the lightning or switching surges’ hazards. Proper surge arresters as well as installation of other mitigation devices are essential from the point of view of reliable working conditions of the transmission and distribution networks. It is difficult to measure such overvoltages because of operational, technological and last but not least – economical issues. However, over the years reliable methods of computational analyses have been developed, which allow one to determine possible overvoltage waveforms in case of different scenarios, such as lightning surges or transformer switching operations.
6 Conclusions
The Insulation Coordination study for a typical system consisting of 380 kV GIS substation interconnected by HV cables has been performed using the EMTP/ATP software. BF and direct stroke scenarios for lightning overvoltage analyses were studied. The overvoltages have been calculated at essential points of the substation: at the transformer HV terminal, substation entrance and substation exit. An alternative solution to the use of an additional GIS surge arrester has been proposed. The passive element consisting of a line trap main coil and a coupling capacitor installed at the portal tower have been introduced. It should be noted that when the HV L–C filter was installed the lightning overvoltages were kept below the BIL, especially in the worst cases where all GIS surge arresters in the power system were not installed. The present paper shows calculations for one particular system. However, considering the proposed solution for other substations and systems will require separate insulation coordination studies to validate its performance for specific conditions
